WO1999063769A2 - Method and radio device for transmitting messages - Google Patents

Abstract

The invention is based on the idea of utilizing the bit groups of a data package that are not needed for allocating said bit groups to a specific logical channel for transmitting the type of information which is specific to said bit group with the purpose of transmitting another type of information, more particularly new signaling information whose importance was not yet recognized when defining the data package or the bit group structure thereof or whose transmission was not yet considered to be necessary when determining the transmission standard.

Description

description

Method and radio for transmission of messages

The invention relates to a method and a radio device for transmitting messages via a communication network, in particular via a mobile radio system and a control device for controlling this transmission.

In order to ensure the most flexible and efficient use of transmission capacities, messages are transmitted in many communication networks in the form of data packets. For example, in a GSM (Global System For Mobile Communication) mobile radio system, messages to be transmitted are packed in data packets, so-called bursts, and then transmitted via the radio interface.

A multiple access method is often used to separate the data packets and to be able to allocate them to a specific connection or the corresponding subscriber. For this purpose, a combination of time division multiple access TDMA and frequency division multiple access FDMA is used in the GSM system. With the FDMA, the frequency band is broken down into several frequency channels of the same size. These frequency channels are divided into eight time slots by TDMA. The eight time slots of this frequency channel are combined into a TDMA frame, the same time slots in successive frames resulting in a physical channel.

These physical channels or the corresponding data packets are assigned to logical channels according to a defined scheme. There are basically two types of logical channels: signaling channels for the transmission of signaling information and traffic channels for the transmission of user data. In order to be able to transmit messages, in particular voice, as efficiently as possible by means of the limited ^" transmission capacities of a radio interface, these messages to be transmitted are compressed by a source code prior to transmission and are protected against channel errors by channel coding. Different methods are known in particular for speech coding. For example, in the GSM system, speech is encoded by means of a full-rate speech codec, a half-rate speech codec or an enhanced full-rate speech codec, these speech codecs or the framework conditions required for this already being known or foreseen during standardization.

Due to the progress in speech coding theory, however, new speech codecs have now been developed which enable an even more efficient and flexible transmission of speech. These are, for example, so-called adaptive multirate speech codecs, the properties of which can be adapted to the transmission properties of the transmission channel. In the context of this application, a speech codec refers to a method for encoding and / or for corresponding decoding, which can also include source and / or channel coding.

In the standardization, definition or definition of a transmission method, in particular the GSM standard, the types of information which are transmitted by means of individual bit positions of a data packet or the purpose of the information transmitted by means of the individual bit positions are precisely defined so that the information at the receiver can be processed and used appropriately.

The basic principle of the invention is now to enable the most efficient and flexible use of limited transmission capacities, in particular within an already existing or standardized one Transmission method and if necessary by means of appropriately standardized signaling channels.

This task is solved by the features of the independent patent claims. Further training results from the subclaims.

The invention is therefore based on the idea of using bit groups of a data packet, which are not required when assigning this bit group to a specific logical channel for transmitting the type of information specific to this bit group, for transmitting another type of information, in particular signaling information, the meaning of which the definition of the data packets or their bit group structure was not yet foreseeable or their transmission was not considered necessary when the transmission standard was defined.

It is thereby achieved that, even after the definition of a transmission method, for example through standardization, new technical developments can be used to improve the use of the transmission capacities.

When the invention is introduced into a transmission method according to the GSM standard, the stealing flag bit group of a normal burst data packet can be assigned, in particular, when the normal burst data packet is assigned to a slow associated control channel for the transmission of new signaling information be used to transmit information about a speech codec used in the transmission of speech data.

This means that more recent developments and knowledge in information and communication technology can also be used to make the transmission of messages more efficient and flexible using a defined transmission method such as the GSM standard. The invention is described in more detail below on the basis of preferred exemplary embodiments, the figures listed below serving to explain them:

Figure 1 is a block diagram of a mobile radio system

Figure 2 is a schematic representation of the assignment of data packets to logical channels

Figure 3 is a schematic representation of a radio

The structure of the mobile radio system shown in FIG. 1 corresponds to a known GSM mobile radio system which consists of a multiplicity of mobile switching centers MSC which are networked with one another or which provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSC are each connected to at least one base station controller BSC, which can also be formed by a data processing system. Each base station controller BSC is in turn connected to at least one base station BS. Such a base station BS is a radio device which can establish a radio connection to radio devices, so-called mobile stations MS, via a radio interface.

The range of the signals of a base station essentially define a radio cell FZ. The allocation of resources such as frequency bands to radio cells and thus to the data packets to be transmitted can be controlled by control devices such as the base station controller BSC. Base stations BS and a base station controller BSC can be combined to form a base station system BSS.

The base station system BSS is also used for radio channel management, data rate adaptation, monitoring of the radio transmission link, hand-over procedures, connection control and the allocation or signaling of the Turning speech codecs responsible and transmits the necessary signaling information to the mobile stations MS. Such signaling information can also be transmitted via signaling channels.

Different data packets are used in the GSM system to transmit information. So-called bursts (data packets), each containing 156.25 bit positions, are transmitted during a time slot. A burst is a period on a frequency carrier or in a frequency channel, which is modulated by a digital data packet. The burst therefore represents the physical content of a time slot.

The data packets differ in their bit group structure. A bit group structure is created by the combination of bit positions within a data packet into bit groups, the combination taking place according to the type of information that is transmitted via the respective bit positions. Each type of information corresponds to a specific purpose for which this information is transmitted. Within the scope of the present application, a distinction can also be made between the following types of information:

- useful information, - signaling information,

Signaling information that is transmitted for a first purpose,

- Signaling information that is transmitted for a second purpose.

This is shown in FIG. 2 by way of example using a normal burst data packet nb, which is used to transmit useful and signaling information by means of the traffic and signaling channels. Of the 148 bit positions bs (the remaining 8.25 bit positions serve as guard period), three tail bits tb are located at the beginning and at the end. In the middle sits a training bit group consisting of 26 bit positions tsb, which are used for The purpose of the synchronization and channel estimation is transmitted, framed by one bit each, which are referred to as the stealing flag bit group sfb. The training bit group separates two coded and usually also encrypted user data bit groups, each with 57 bit positions cnib.

In addition to the normal burst data packet nb, in the downlink (BS-> MS) there is also the frequency correction burst fb, which is used for frequency synchronization of a mobile station MS, and the synchronization burst, which i.a. Transmits information on the time synchronization of the mobile station with the base station, and in the uplink (MS-> BS) the access burst which is used for the first access of the MS to the BS if there is still no two-way connection.

There are two basic types of logical channels: signaling channels for the transmission of signaling information, such as the slow-associated control channel sacch or the broadcast control channels, and traffic channels tch for the transmission of user data.

FIG. 2 shows the assignment of different data packets fb nb to logical channels, such as a slow-associated control channel sacchl or to traffic channels tch4 tchl. This assignment is made in accordance with the assignment of the physical channels to the logical channels.

Each traffic channel tch 1 is assigned a slow-associated control channel sacch 1, by means of which adjacent channels in the downlink for the transmission power adjustment, frame alignment and channel numbers can be continuously monitored, and in the uplink signaling information about reception level (ie signal strength) and bit error rates (ie reception quality) become. Usually, the normal burst data packets are assigned to traffic channels ^' tch, the stealing flag bit group sfb being used for the transmission of signaling information to indicate whether a normal burst data packet nb intended for the transmission of user data is exceptionally for urgent signaling purposes are used or “stolen” (purpose of the stealing flag bit group sfb).

The signaling information of the slow-associated control channel sacch is also generated using normal burst

Transfer data packets nb. However, in the case of the sacch, the exceptional use of the corresponding normal burst data packets nb for the transmission of urgent signaling information is not permitted. The stealing flag bit group sfb can therefore not be used in this case to transmit the type of information specific to it and is therefore actually superfluous in this case. In this case, therefore, a "1" is transmitted as a standard at these two bit positions sfb.

So far, a half-rate speech codec, a full-rate speech codec and an enhanced full-rate speech codec have been provided as speech codecs for the GSM system. For the transmission of signaling information about the speech codec to be used or used for a connection or traffic channel tch, corresponding signaling channels or bit positions have already been defined during the standardization.

In the future, messages should also be able to be transmitted via the GSM system using new and improved voice codecs. A group of novel speech codecs, so-called adaptive multirate (AMR) speech codecs, is currently being standardized at ETSI SMG11. Combined source and channel coding can also be carried out.

The main goals of the AMR speech codec are to achieve fixed network quality of speech under different channel conditions and ensure optimal distribution of channel capacity. The speech codec should work under good channel conditions and / or in highly utilized cells in the half-rate (HR) channel. Under poor channel conditions, it should be able to switch dynamically to the full rate (FR) channel using the GSM intra-cell handover and vice versa. Within a channel mode (FR or HR), several code modes (code mode) are available for different speech and channel coding rates, which also vary from one to the other according to the channel quality. This should result in the best speech quality taking into account the changing channel conditions.

In principle, there are two methods of transmitting this newly added signaling information for switching between the group of the now existing speech codecs (FR, HR and EFR) and the future AMR speech codecs:

in-band by means of additional bit positions bs, which would otherwise lead to better voice transmission;

- Out-of-band using a signaling channel.

Above all for a tandem free operation (TFO), in which format conversions can be avoided when transmitting the speech from one GSM system to another, for example via a PSTN, the aim is to switch between the group of speech codecs (FR.) That now exist , HR and EFR) and the future AMR speech codecs out-of-band.

In order to be able to transmit information about a new improved speech codec to be used or used for a traffic channel tchl, the stealing flag bit group sfb of a normal burst data packet nb, which is assigned to the corresponding slow-associated control channel sacchl, is now used is used for out-of-band signaling using speech codecs. When an AMR speech codec is used in the traffic channel tchl, a "0" is transmitted at the bit positions of the stealing flag bit group sfb of the corresponding slow-associated control channel sacchl, thereby signaling the use of an AMR speech codec. If the previous speech codecs (ER, HR, EFR) are used, a "1" is transmitted at the bit positions of the stealing flag bit group sfb.

In one embodiment variant of the invention, it is sufficient to transmit information that a voice codec (ER, HR, EFR) other than one previously defined for the transmission method is used. Detailed information about the new speech codec can be packed into the transmitted user data by means of the new speech codec or can be transmitted instead of it.

In another embodiment of the invention, detailed information about the new speech codec can be transmitted by certain combinations of the bit position assignment ("0 1" or "l 0") of the stealing flag bit group sfb, or also the stealing flag bit groups sfb of successive data packets .

In order to protect this signaling information against channel errors by using a new speech codec, it can additionally be channel-coded. Since the switchover from an AMR speech codec to a previously known speech codec (e.g. EFR) or vice versa is very slow, a relatively long delay in the switchover is unproblematic.

The corresponding signaling information can therefore be transmitted by means of a plurality of successive normal burst data packets assigned to a sacch. For example, an affected stealing flag bit can be channel encoded at a rate of 1/6 and the resulting six code bits can be divided into three consecutive ones a normal burst data packets assigned to a slow-associated control channel sacch are transmitted.

Based on the present description, the invention can also be used for signaling other information, such as switching information, in other transmission methods, such as DECT, WB-CDMA or multimode transmission methods (GSM / WB-CDMA / TD-CDMA), and the corresponding signaling channels be used.

FIG. 3 shows a radio which can be a base station BS or a mobile station MS. It consists of a control device STE and a processing device VE, a power supply device SVE, a high-frequency part HF consisting of a receiving device EE, a transmitting device SE and a frequency synthesizer SYN and an antenna device ANT. The individual elements of the radio are also connected to one another by conductor tracks, cables or bus systems.

The control device STE essentially consists of a program-controlled microcontroller and the processing device VE consists of a digital signal processor, both of which have write and read access to memory modules. The microcontroller controls and controls all essential elements and functions of the radio and essentially controls the communication and signaling process, the combination of bit positions into bit groups and the assignment of data packets to logical channels.

The digital signal processor, a part of the digital signal processor or a special processor is responsible for performing the speech coding or speech decoding. The microcontroller controls the selection of the speech codec as a function of received signaling information. Analog / digital converters convert the analog audio signals and the analog signals from the high-frequency part HF into digital signals and process them by the digital signal processor. After being combined into data packets, the digital signals are converted back into analog audio signals and analog signals to be supplied to the high-frequency part HF by digital / analog converters. For this purpose, modulation or demodulation is carried out, if necessary.

Claims

claims 1. Method for the transmission of messages, in which a) the transmission is based on data packets (nb) b) a data packet has several bit positions (bs) to which different types of information (tb, cnib, sfb, tsb) are assigned , c) by an information type-specific combination of bit positions into bit groups within a data packet Bit group structure arises, d) data packets of the same bit group structure are assigned to different types of logical channels (sacchl, tch4, tchl), and e) a bit group (sfb) of a data packet (nb), which is assigned to a logical channel (sacchl) for transmission which is not required for the specific type of information is used to transmit another type of information. 2. The method according to claim 1, in which a) the transmission method is based on the GSM standard or a standard derived therefrom, b) the stealing flag bit group (sfb) of a normal burst data packet (nb) when assigning the normal -Burst data packet (nb) to a slow-associated control channel (sacchl) is used to transmit information other than that specific to them. 3. The method according to any one of the preceding claims, in which the stealing flag bit group (sfb) of a normal burst data packet (nb) in the assignment of the nor al-burst data packet (nb) to a slow-associated control Channel (sacch) for the transmission of signaling information via the speech codec, which is used in the transmission of data via the traffic channel (tchl) associated with this slow-associated control channel (sacchl). 4. The method according to any one of the preceding claims, in which an adaptive multirate speech codec can optionally be used as the speech codec for a traffic channel in addition to a half-rate speech codec and / or a full-rate speech codec and / or an enhanced full-rate speech codec can. 5. Radio (MS) with a) means for transmitting messages on the basis of data packets, a data packet having a plurality of bit positions to which different types of information are assigned, and a bit group structure resulting from an information type-specific combination of bit positions into bit groups within a data packet , b) means for assigning data packets of the same bit group structure to different types of logical channels, and c) means for using a bit group of a data packet which is not required for the assignment to a logical channel for transmitting the type of information specific to them Transfer of another type of information. 6. Radio (MS) according to claim 5 with a) means for transmitting messages based on the GSM standard or a standard derived therefrom, and b) means for using the stealing flag bit group one Normal burst data packet when assigning the normal burst data packet to a slow-associated control channel for the transmission of information other than that specific to it. 7. Radio (MS) according to one of claims 5 to 6 with means for using the stealing flag bit group of a normal burst data packet when assigning the normal burst data packet to a slow-associated control channel for the transmission of Signaling information about the voice codec that is used for the transmission of voice data over the traffic channel assigned to the slow-associated control channel is used. 8. Radio (MS) according to one of claims 5 to 7 with means for speech coding on the basis of the half-rate Speech codecs and / or the full-rate speech codec and / or the enhanced full-rate speech codec or optionally an adaptive multirate speech codec is carried out. 9. Control device (BSC), which is assigned to one of the radio devices (MS) according to one of claims 5 to 7 for controlling the transmission of messages.